Mohamed Mohamud in federal court in Portland after his arrest.Sketch by Abigail Marble

The terrorism case against Portland bomb-plot suspect Mohamed Mohamud took a curious turn Wednesday when a federal judge closed his courtroom to the public so lawyers could argue over video footage of two undercover FBI operatives.

U.S. District Judge Garr M. King opened the hearing to listen to arguments on an array of issues involving the government's evidence in the case.

Mohamud, 21, is suspected of attempting to set off a bomb at Portland's 2010 holiday tree lighting ceremony. His lawyers have mounted an entrapment defense.

Assistant U.S. Attorney Ethan D. Knight, who heads the prosecution of Mohamud, told King that the government has turned over "voluminous" written records to the defense and would declassify and turn over more in coming weeks.

Then, 25 minutes into the hearing, King closed the courtroom to all but people involved in the prosecution or defense of Mohamud, who is charged with attempting to ignite a weapon of mass destruction. Mohamud, whose trial is set for January, is being held in the Justice Center jail in downtown Portland.

In a pretrial filing, prosecutors asked King to take extraordinary steps to protect the identities of the two undercover operatives who befriended Mohamud as part of the FBI's sting.

The government wants to sneak the operatives in and out of the courthouse, put them in light disguise, obscure their faces in video footage, prohibit the defense from asking questions that might reveal personal information about them and require news media to hear -- but not view -- their trial testimony on a closed-circuit TV feed from another room.

Mohamud's defense team has argued in court filings against most of the requests.

It's unclear what the legal teams argued behind closed doors and it's unclear whether King ruled on any of the motions before him. The judge declined, through court staff, to speak to The Oregonian at the conclusion of the hour-long hearing.

"Judges have a great deal of discretion when it comes to protecting national security interests and undercover operations that affect national security," said Portland defense lawyer Bob Weaver, a former federal prosecutor.

Peter Bhatia, editor and vice president of The Oregonian, noted that openness should be the norm in courtrooms. "We respect, of course, the authority of federal judges in their courtroom, especially if national security is perceived to be involved, but would like to know more about the necessity in this case," he said.